Environment and Breast Cancer: Science Review

Evidence From Humans
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Cancer Mortality Risks from Long-term Exposure to Ambient Fine Particle
Wong, C. M., Tsang, H., Lai, H. K., Thomas, G. N., Lam, K. B., Chan, K. P., Zheng, Q., Ayres, J. G., Lee, S. Y., Lam, T. H., Thach, T. Q. Cancer epidemiology, biomarkers & prevention : a p. 2016. 25:5, 839-45.
Topic area
Environmental pollutant - Air pollution Vehicle exhaust
Study design
Prospective cohort
Funding agency
Wellcome Trust This article is officially marked a
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Analyses restricted to individuals aged 65 years or older.
Number in Cohort
Cohort: 60,273 men and women
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
66,820 men and women aged 65 and older were recruited on a voluntary basis from 18 Elderly Health Centres in Hong Kong between July 1998 to December 2001. Vital status including breast cancer mortality was ascertained by record linkage to Hong Kong death registries through 2011. Ten percent of the cohort was excluded from analysis because of missing covariate data. The number of women in the cohort is not stated.
Exposure Investigated
Exposures investigated
Average annual residential exposure to PM2.5 was modeled for each geocoded address during recruitment (1998-2001) Estimated were based on vertical height of residence above sea level, satellite data, and hourly PM2.5 concentrations from five monitoring st
How exposure was measured
GIS/geographic Environmental sample
Exposure assessment comment
It is not stated whether address was reported by participants or obtained from medical or other records.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Individual: Age, gender, BMI, smoking status, exercise frequency, education level, and personal monthly expenditure. Ecological (from census): percentage of older subjects, percentage with tertiary education, and monthly domestic household income. Envir
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked Yes. No, if not.
Strength of associations reported
Female breast cancer mortality, per 10 μg/m3 increase in PM2.5:
Overall: aHR 1.80 (95% CI 1.26-2.55)
Among never smokers: aHR 1.66 (95% CI 1.10-2.50)
Amon ever smokers: aHR 7.14 (95% CI 2.01-25.4)
Results Comments
p-interaction for smoker status = 0.10 Reported HRs are for women only, but the number of female participants is not specified.
Author address
School of Public Health, The University of Hong Kong, Hong Kong. Institute of Applied Health Research, University of Birmingham, Birmingham, United Kingdom. thach@hku.hk g.n.thomas@bham.ac.uk. Nuffield Department of Population Health, University of Oxford
Reviewers Comments
Mortality is not a sensitive measure of breast cancer risk. It is not clear whether or how the authors determined when individuals moved out of the study area. They note that follow-up was primarily through the death registry, and that individuals not in the registry were assumed to be alive at the end of follow-up. The effect estimate from a sensitivity analysis for all cancer mortality, excluding the 16% of individuals they considered "potentially lost to follow-up" was similar to the main analysis for all cancer mortality, however no sensitivity analysis was performed for breast cancer mortality in particular.